What Is FeNO Testing?

FeNO stands for Fractional Exhaled Nitric Oxide. It is a simple breath test that measures the level of nitric oxide in the air you breathe out, which is a marker of a particular type of airway inflammation linked to asthma. The test takes only a few minutes, uses no needles, and needs no recovery time.

In people with asthma, the airways are often inflamed, and this inflammation tends to raise the level of nitric oxide in the breath. By measuring it, a FeNO test gives your consultant objective information about whether airway inflammation is present and how it is responding to treatment - detail that a standard lung function test alone cannot provide.

FeNO testing is recommended by NICE (the National Institute for Health and Care Excellence) as a first-line objective test in the asthma diagnostic pathway [1]. At LivingCare Leeds, it is offered as part of a respiratory consultation, giving our consultants immediate, objective information to support an accurate diagnosis and a personalised plan.

What Can FeNO Testing Tell Us?

FeNO measurement is a useful clinical tool across a range of situations:

• Diagnosing asthma - a raised FeNO result alongside typical symptoms supports an asthma diagnosis, while a normal result may point towards an alternative cause [1]
• Monitoring asthma control - in people with a known diagnosis, FeNO can indicate whether airway inflammation is well controlled or whether treatment may need adjusting [1]
• Guiding inhaled steroid therapy - FeNO can help your consultant decide whether to start, increase, reduce or continue inhaled corticosteroid treatment [1]
• Identifying steroid responsiveness - a high FeNO result often predicts a good response to inhaled corticosteroids, which is helpful when planning treatment [1]
• Reviewing inhaler use - a persistently raised FeNO in someone on inhaled steroids may prompt a review of how, or whether, the medication is being taken [1]

How Does the FeNO Test Work?

The FeNO test is quick and straightforward. Most people find it easy, though the controlled breathing takes a little practice for some. It usually takes only a few minutes and involves three simple steps.

Step 1 - Preparation. You will be asked not to eat, drink anything other than water, or exercise vigorously for at least one hour beforehand, as these can temporarily affect nitric oxide levels. You should keep taking your regular medications unless your consultant advises otherwise.

Step 2 - The Breath Test. You breathe in deeply, then exhale slowly and steadily into a handheld FeNO analyser for around 10 seconds, keeping a controlled flow. You may need a little practice to hold a steady breath, and our team will guide you through it. The device measures the nitric oxide in your breath in real time.

Step 3 - Immediate Results. Your reading is available straight away. Your consultant will review it alongside your full clinical history and any other test results to build a complete picture.

What to Expect at Your FeNO Appointment

FeNO testing at LivingCare is performed as part of a respiratory consultation rather than as a standalone test. That way your result is always interpreted by a specialist in the context of your symptoms and history - not treated as an isolated number.

Your appointment begins with a clinical consultation with our respiratory consultant, who will review your symptoms, history and any existing results. The FeNO test is then carried out, and the reading is discussed with you during the same appointment. A written report summarising the consultation, your FeNO result and the recommended next steps is provided to you and, with your consent, sent to your GP.

Who Should Consider FeNO Testing?

FeNO testing may be particularly helpful if you:

• Have symptoms that could suggest asthma - such as wheeze, cough, breathlessness or chest tightness [2] - but have not yet been formally assessed
• Have been told you have asthma but are unsure whether the diagnosis is correct
• Have asthma that is not well controlled despite treatment, and want to understand whether airway inflammation is playing a part
• Are considering starting, stopping or adjusting inhaled corticosteroid treatment and want objective evidence to guide the decision

Because FeNO is one part of a fuller assessment, a respiratory consultation is the right place to work out whether the test is useful in your case.

Risks and Considerations

FeNO testing is non-invasive and generally well tolerated. There are no needles and no recovery time, and there are no known risks from the test itself. Some people need a little practice with the controlled breathing technique - our team will talk you through it and make sure you are comfortable before you begin.

It is important to know that FeNO is one part of a full clinical assessment. It is not used on its own to diagnose or rule out asthma [1]. Your consultant will interpret your result alongside your symptoms, lung function and clinical history to reach the most accurate conclusion.

Why Choose LivingCare for FeNO Testing in Leeds

At LivingCare in Leeds, FeNO testing is delivered by our consultant-led respiratory team at our Thorpe Park clinic - part of our wider respiratory medicine service. You get fast, consultant-led access with no GP referral needed, self-pay or insurance, and your result is always read by a specialist in the context of your symptoms rather than handed back as a bare number.

This is exceptional care, without the wait - a clear explanation of what your result means, a written report for you and your GP, and a plan for what happens next.

To arrange an assessment, book your consultation online.

References

1. NICE - Asthma: diagnosis, monitoring and chronic asthma management (NG245), Recommendations
2. NHS - Asthma